<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        .login{
            display: none;
            width: 512px;
            height: 280px;
            position: fixed;
            border: #ebebeb solid 1px;
            left: 50%;
            top: 50%;
            background-color: #fff;
            box-shadow:  0 0 20px #ddd;
            z-index: 9999;
            transform: translate(-50%,-50%);
        }
        .login-title {
            width: 100%;
            margin: 10px 0 0 0;
            text-align: center;
            line-height: 40px;
            height: 40px;
            font-size: 18px;
            position: relative;
            cursor: move;
        }
        .login-input {
            overflow: hidden;
            margin: 0 0 20 0;
        }
        .login-input-content {
            margin-top: 20px;
        }
        .login-button {
            width: 50%;
            margin: 30px auto 0px auto;
            line-height: 40px;
            font-size: 14px;
            border: #ebebeb 1px solid;
            text-align: center;
        }
        .login-bg {
            display: none;
            width: 100%;
            height: 100%;
            position: fixed;
            top: 0;
            left: 0;
            background-color: rgba(0,0,0,.3);
        }
        a {
            text-decoration: none;
            color:#000000;
        }
        .login-button a {
            display:block;
        }
        .login-input input.list-input {
            float: left;
            line-height: 35px;
            height: 35px;
            width: 350px;
            border: #ebebeb 1px solid;
            text-indent: 5px;
        }
        .login-input label {
            float: left;
            width: 90px;
            padding-right: 10px;
            text-align: 35px;
            font-size: 14px;
        }
        .login-title {
            position: relative;
            width: 100%;
            margin: 10px 0 0 0 ;
            text-align: center;
            line-height: 40px;
            height: 40px;
        }
        .login-title span {
            position:absolute;
            font-size: 12px;
            right: -20px;
            top: -30px;
            background-color: #fff;
            border: #ebebeb solid 1px;
            width: 40px;
            height: 40px;
            border-radius: 20px;
        }
    </style>
</head>
<body>
    <div class="login-header"><a id="link" href="javascript:;">点击,弹出登录框</a></div>
    <div id="login" class="login">
        <div id="title" class="login-title">登录会员
            <span><a id="closeBtn" href="javascript:void(0);" class="close-login">关闭</a></span>
        </div>
        <div class="login-input-content">
            <div class="login-input">
                <label>用户名:</label>
                <input type="text" placeholder="请输入用户名" name="info[username]" id="username" class="list-input">
            </div>
            <div class="login-input">
                <label>登录密码:</label>
                <input type="password" placeholder="请输入登录密码" name="info[password]" id="password" class="list-input">
            </div>
        </div>
        <div class="login-button" id="loginBtn"><a href="javascript:void(0);" id="login-button-submit">登录会员</a></div>
    </div>
    <!-- 遮罩层 -->
    <div id="bg" class="login-bg"></div>
    <script>
        //1.获取元素
        var login = document.querySelector('.login')
        var mask = document.querySelector('.login-bg')
        var link = document.querySelector('#link')
        var closeBtn = document.querySelector('#closeBtn')
        // 点击弹出层这个链接 link 让mask 和 login 显示出来
        link.addEventListener('click', function(){
            login.style.display = 'block';
            mask.style.display = 'block';
        })
        // 点击关闭按钮closeBtn 让mask 和 login 隐藏

        closeBtn.addEventListener('click', function(){
            login.style.display = 'none';
            mask.style.display = 'none';
        })

        // 页面中拖拽的原来:鼠标按下 mousedown 并鼠标移动 mousemove 之后 松开鼠标mouseup
        // 拖拽过程 鼠标移动过程中 获得最新的值赋值给模态框的left 和top值 这样模态框就能跟着鼠标走了
        // 鼠标按下触发的事件源是最上面一行 就是id 和 title
        // 鼠标的坐标减去鼠标在盒子内的坐标 才是模态框的真正位置

        // 鼠标按下 获得鼠标在盒子内的坐标
        var title = document.querySelector('#title');
        title.addEventListener('mousedown', function(e){
            var x = e.pageX - login.offsetLeft
            var y = e.pageY - login.offsetTop;
            // 鼠标移动 在鼠标的页面中的坐标,减去鼠标在盒子内的坐标就是模态框的left 和top 值
            document.addEventListener('mousemove', move)
            function move(e){
                login.style.left = e.pageX - x + 'px'
                login.style.top = e.pageY - y + 'px'
            }
            // 鼠标弹起,就让鼠标移动移除
            document.addEventListener('mouseup',function(e){
                document.removeEventListener('mousemove',move)
            })
        })
    </script>
</body>
</html>